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Re: uo-36 tnc's

Hi Randy and the Group,

Sorry for the delay in reply, I am having some bad days in my health so I am 
making the most of a few good hours to answer some of the questions.

> What will you do if we end up with satellites on 38k4, 76.8 and 153k6? Will
> you switch between 3 IFD boards or just use the fillers for 153k6. Doing so
> will require 6 db more gain in your ground antennas than you really need for
> 38k4.

I believe that you can only fit one IFD board in the radio, though I am sure 
that Ulf Kumm could answer you better than I. At the moment the IFD board is 
set to 38,400 to 76,800 baud bandwidth, so the next jump we will make will 
need no adjustment to the system. The modem I believe will need a few 
components changed and then we will be up and running on the new speed. 
Already Symek are addressing some new issues that we thought for the next 
generation but this information will be release at a later date. The TNC3S is 
good upto 1.6 mbs from what I understand, and it will have no problems 
dealing with that. I know a lot of people are worried that Serial Port are 
going to be history soon as many of the technical meetings of manufactures 
have stated. The TNC3S are able to make use of a different interface and I am 
sure that Symek is already working on the next generation interface too.
>Are the large Oscar antennas that much of an over kill for 38k4?

I use a 38 element Tonna which is adequate as long as the Polarisation is 
right, my antenna is fixed to RHCP, having a switching system would be far 

>What are the smallest gain antenna needed for UO-36 at 38k4?

Not sure really, I would not use less than 12 element in any plain.

>The other limitation is the connection speed between the TNC and the 
>computer. I have used a PacComm Spirit-2 to receive 38k4 from 
>UO-36 but its top RS-232 speed is 57.6 kb. The top speed of the 
>Symek TNC3S is 115.3 kb.  I think that a satellite using the PacSat 
>broadcast protocol with 153k6 downlink would overrun the TNC to 
>computer link.

I agree with you, the biggest hurdle we all see these days is the link 
between computer and TNC, Chris Jackson saw this and decided to use a WANic 
card using HDLC format, but this is a very expensive route to take when you 
start with figures of $600 to $800 each, and no software wrote for Windows 
95, 98, or Dos just Windows NT. Running the RS-232 speed at 57.6 kb for the 
PacComm is ok for the 38,400 baud as there is less chance of an over run in 
the buffers. If you run the terminal baud speed at 38,400 baud we found many 
errors, so the higher speed on the computer - TNC the better. If there is a 
need to increase the terminal baud speed above the 115k6 than I am sure that 
Symek will address that very capably as they have already done whilst we were 
all beta testing the present system.

>You could use the option on the TNC3S to use the serial port not as an RS-232
>port but as a link to a HDLC card in the PC. If you have such a card then it 
>is just as easy to attach the modem cards direct to it and skip the TNC.  In 
>any case I do not believe that WISP supports a HDLC card.

I cannot remember what other interface is available as I type this e-mail, 
but I know that the TNC as been used as a NET Node without the serial port 
been there, so there is always another solution with this generation of TNC. 
I had already spoken with Symek and we had talked about higher internal 
speeds greater than 20 MHz, the interface like Ethernet must be a simple 
option, and possible USB in their possibly too.

>I am still ready to order a TNC3S to experiment just how fast we can go.

I believe that you will not be disappointed, not of the members that have 
moved to this next generation of speed or satellite have complained, in fact 
many were stunned at what the difference this speed can make to downloading 
large files or complex images.
>What would I like to see from Symek and others?
>1. A high speed modem whose speed can be software select 
>between           38k4,  76k8 and 153k6.

I am sure that in future ideas a model might be made, but with DSP it is a 
hard task because of the many thousands of instructions. Once people in the 
satellite manufacture make the system work, then I am sure they will help the 
people on the ground create a better system for us too.
>2. A USB interface to the TNC3s with WISP supporting it.
>                 or
>WISP support of a HDLC (with DMA) card in the PC.

I have already make the request for the USB whilst we was in the first stages 
of beta testing the current system, Symek and make other involved then also 
make several comments on the same lines. If it is possible you can guarantee 
that Symek will make it work for us. On the HDLC system, this is already in 
use in Surrey's command station, I have no idea how hard it would be for 
Chris Jackson to make it work for the user WiSP, but if the need arises I am 
sure Chris Jackson will go the extra mile too as he did for this last 
innovative jump.

>3. More amateur high speed birds in the sky.

I believe that your wish might have already been granted, there is a few 
satellites in the final stages of development that can work these speeds and 
all of the later UoSat satellites are capable of 76,800 baud. Now that we 
have managed to break the mould of the limitation of our receivers, we should 
be able to go all the way to the next limit of 153k.
> What am I working on?
>I am looking at doing my own modem design with selectable speeds
> (19k2,38k4,57.6 and 153.6).

This is good news, as long as you can make the modem switchable by either 
software or by external device then you might have a winner
>I am writing my own software to support a HDLC card that will
>be a PacSat file server.

This might be an ideal solution for the satgate Randy, good luck with your 
>Using the above software and a 153.6 modem to send JPEG files
>down on S-Band (2 watts) on a satellite to be launched next year.

The higher in frequency we go the better the results we should have, the 
lower bands are too crowded these days, Surrey University I believe had some 
very good results with UO-36 on L & S band.
>Looking at a follow on satellite that will drop all this high speed 
>FSK stuff and change over to QPSK, FEC, and encoding 
>schemes for a new generation of high speed amateur LEO 

I think that HDLC might be a good place too, a lot of work recently might 
prove that HDLC is a better link than we have currently. Good luck with the 
idea, but I think we are in the trap of following the makers of the 
satellites rather than us making a few requests. I have had a few ideas 
myself and I am sorry to say that my health as but pay to many of these for a 
few years.
>Will P3D stick with FSK?  It believe it can support other modulation schemes.

No, I know that the folks over in Germany have several ideas they want to 
test and I fully expect that when they are ready and have a fully functional 
satellite in orbit they will help us understand some of these experiments 
like QPSK, BPSK.
> It was great watching 38k4 from JAWSAT before it was launched.

I am sure it was, to see those files come off the satellite and into your 
computer is hard to contain yourself, internet speeds in our hobby was a 
dream a few years ago, now it is a reality thanks to many people behind the 
scenes. Already we are starting to see new ideas of ways to improve on the 
current systems, they may take a few more months or even a year, but from now 
we are going to increase data rates at low cost rather then us pay those 
awful commercial prices.

>I may get on more but I expect to be experimenting with 153k6 in the next 
>few months.

Randy, whether is takes you a month or a few months we will all be happy to 
see your callsign on the satellite, the more the merrier as it shows the 
makers that we are willing to make that extra effort to achieve there's and 
our dreams.

>I need to fix my rotors too but I thought you had to wait for winter to do 
>those projects. Also I have to replace the backup battery in my Trakbox 
>it keeps moving my QTH around the world when I turn it off.

I think this past few years the weather as hit our antenna systems the 
hardest, freak storms, extreme rain and high temperatures have paid a heavy 
price and this year as seen more amateurs repairing or maintaining their 
systems than in other years. At least it will be warm when I maintain my 
rotors this time, I just hate freezing to metal in winter months, Hi.

>Thanks Chris, Jeff and others for pushing the digital speed.  I just wish 
>we could get WO-39 back up and running 38k4. Look for a new satellite 
>with 153k6 next year.

It would be an excellent thought to see WO-39 working at 38k4 Randy, I do 
hope that you can recover her to those speeds. The new satellite sounds even 
better, people just hate it when I tell them I have a high speed data link to 
the outside world that does not go down the telephone line.

I used my early work during the beta stages to beat cancer, the hobby can be 
very powerful when you have something to concentrate on and this move to 
higher speeds was something that I could get my grey cells working on to help 
the process. The more we break the front-end of technology, the more we have 
to offer the world as a whole, there will always be a threat from the 
commercial world but without us there would never be those ideas tested at 
low costs and beta testing with sure a highly knowledgeable international 
forum. I am sure that each of us as a lot to offer, just that we are now we 
are making a major leap again.

Take care Randy, good luck with the projects and don't forget to let us all 
know if we can help you achieve those goals. I will be incommunicado until 
Friday as I am back to hospital to see my favourite oncologists, but if you 
want to ask any questions, please be my guest and fire away.

Take care Everyone, good luck if you are about to try this new digital speed 
or any other project you might be working on.


Chris J. Dixon
Member of AMSAT-UK & RSGB
South Wales, UK.

My own web page: http://members.aol.com/cdixon6901/
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